The present invention relates to a multi-segment light-emitting diode (LED), and particularly to a new type of incoherent LED suitable for point-to-point communication functions.
As shown in FIG. 1, a conventional LED communication link includes a LED transmitter 10 that emits a broad radiative angle beam 12. When a receiver 14 detects the presence of the beam 12, the communication link has been established.
The design of LED communication channels presents two contradictory requirements. The first requirement is that broad beam coverage is necessary to simplify pointing and to reduce sensitivity to pointing direction. The second requirement is the necessity of low power usage to increase battery life. Broad beam coverage requires significantly more power than narrow beam coverage. Lower power usage reduces beam coverage. These contradictory requirements are traditionally solved by a compromise between the beam coverage and the power usage based on the intended application.
There are multiple references that use segmented LEDs or a plurality of LEDs to form a single beam. None of these references, however, solve the problem of providing broad beam coverage without significantly increasing power usage. The references discussed individually below do not solve this problem, but some attempt partial solutions to the problem or, although not directed to this problem, teach structure that could be used to solve it. For example, U.S. Pat. No. 5,359,448 to Laszlo et al. is directed to a transmitter that can provide broad beam coverage, but does not deal with the issue of power consumption. U.S. Pat. No. 5,191,461 to Crawshaw et al., U.S. Pat. No. 5,212,707 to Heidel et al., and U.S. Pat. No. 5,594,752 to Endriz deal with increasing signal power using multiple illumination sources, but do not deal with broad beam coverage or power consumption. U.S. Pat. No. 5,317,170 to Paoli discloses using an array of independently addressable LEDs, that are used to provide a display. None of the references, however, solve the problem of broad beam coverage with low power consumption.
U.S. Pat. No. 5,359,448 to Laszlo et al. is directed to an infrared signal transmitter that may be used for amplifying and transmitting signals to an infrared signal receiver in a hearing device for the hearing impaired. Laszlo et al. disclose the use of a plurality of individual infrared transmitting elements sharing a protective cover. To change arrays or patterns the transmitter head must be removed and replaced. Depending on the array or pattern, broad beam coverage could be achieved.
There is, however, no explicit provision for reducing power consumption.
U.S. Pat. No. 5,191,461 to Crawshaw et al. is directed to a transceiver device that uses multiple LEDs in a line to increase signal strength. More specifically, Crawshaw et al. describe an infrared network transceiver that includes illumination sources such as a plurality of infrared LEDs arranged in a line. The illumination sources are aimed and projected in a predetermined orientation onto a reflective planar surface. Once properly positioned, the Crawshaw et al. device includes means for maintaining the predetermined orientation. The focus of this patent is increasing beam intensity, and beam coverage and power are not dealt with in this reference.
U.S. Pat. No. 5,212,707 to Heidel et al. is directed to an array of diffraction limited lasers and a method of aligning the diffraction limited lasers. The purpose of the Heidel et al. device is to provide a single spot of high intensity laser output using a standard power supply. To accomplish this, Heidel et al. disclose one-dimensional and two-dimensional arrays of laser diodes, each laser diode having an associated lens assembly. A refractive lens and a one-dimensional array of binary optical elements are used to focus the emissions of the lasers to produce a single spot of high intensity light. Multiple one-dimensional arrays may be clamped together to form two-dimensional arrays. This reference specifically teaches away from producing a larger, less intense broad beam laser output.
U.S. Pat. No. 5,594,752 to Endriz discloses a diode laser source with concurrently driven light emitting segments. Endriz discloses the use of a plurality of concurrently driven laser segments which focus on a single overlapping spot. Like the Heidel et al. reference, this reference specifically teaches away from producing a larger, less intense broad beam laser output.
U.S. Pat. No. 5,299,219 to Hayakawa is directed to a stripe-type laser diode used as a light source. This high-powered laser diode includes a one-dimensional array of independently operating narrow beam stripe lasers, a configuration which is said to minimize phase locking. All of the lasers are pointed in the same direction. To accomplish a high-power laser diode that has a wide emitting aperture and good stability, a plurality of internal waveguides are connected to a single xe2x80x9cwidexe2x80x9d waveguide.
U.S. Pat. No. 5,317,170 to Paoli discloses high density, independently addressable, surface emitting semiconductor laser/light emitting diode arrays without a substrate. Specifically, the patent is directed to a fabrication technique for constructing an array of emitting regions with individual contacts, supplemented by an optional fresnel or micro lens array to modify the surface emitted light. The use of multiple magnifying micro lenses in an array all pointed forward creates the effect of a larger image, such as would be appropriate for use as a display device or LED panel.
U.S. Pat. No. 5,663,581 to Holm et al. is directed to an implanted LED array and method of fabrication. Like the Paoli reference, the Holm et al. reference discloses an LED array and method of fabrication that would most likely be used for a display device or to create a display device.
The multi-segment LED with azimuthal intensity control of the present invention combines conservative power usage and broad beam coverage. In one preferred embodiment beam steering is used to achieve low power usage. In an alternate preferred embodiment, using beam steering and providing extra power to the resulting steered beam, conservative power usage is achieved. The LED of the present invention could be used in such exemplary devices as remote control devices, hand-held computers, and cameras that rely on infrared links for communication functionality.
The present invention is directed to a power conservative multi-segment LED transmitter including a multi-segment LED with a plurality of independently addressable LED segments, each LED segment suitable for selectively emitting a beam segment. A controller selectively enables and disables the LED segments.
In one preferred embodiment of the present invention, the controller selectively enables and disables LED segments so that the respective emitted beam segments from the enabled LED segments together form a low power steered beam.
In a separate preferred embodiment of the present invention, the controller selectively enables and disables LED segments, but provides high power to the enabled LED segments so that the respective emitted beam segments from the enabled LED segments together form a power conservative steered beam that uses no more power than that required by enabling all the LED segments on low power.
In yet another separate preferred embodiment of the present invention, the LED segments are directed so that an overlapping beam pattern is formed. In this embodiment the controller selectively enables or disables LED segments so that the result is either an overlapping low power intense steered beam or, by providing extra power to the enabled LEDS, an overlapping power conservative steered beam consuming substantially no more power than the power consumed by the overlapping beam.
A steerable multi-segment LED transmitter and receiver system of the present invention, in a separate alternate preferred embodiment, includes a plurality of states: an xe2x80x9call enabledxe2x80x9d state in which each of a plurality of independently addressable LED segments of the multi-segment LED are enabled and emit a respective beam segment; a xe2x80x9ctrainingxe2x80x9d state in which the LED segments are selectively enabled and disabled and the receiver determines substantially detected beam segments; and a xe2x80x9csteeredxe2x80x9d state in which only the LED segments emitting the substantially detected beam segments are enabled.